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To plug and protect
Published:  13 July, 2017

US Department of Homeland Security reveals innovative solution to protect critical infrastructure from flooding (video available)

The solution takes the form of a giant inflatable plug that according to the DHS’ Science and Technology Directorate will seal off subway tunnels and stop water from flowing throughout the subway system into stations and other subway lines.

The so-called Resilient Tunnel Plug was demonstrated at a recent event in Frederica, Delaware, by manufacturer ILC Dover, the Department of Energy’s Pacific Northwest National Laboratory, and West Virginia University.

The uninflated plug integrates seamlessly into a subway tunnel without impeding the flow of normal train traffic, but can be quickly inflated to stop water from rushing through the tunnel and remain inflated to withstand the incredible pressure of restrained floodwaters.

“The project started with a simple proof of concept to demonstrate feasibility," said Greg Holter of PNNL. “We then moved into the development phase to design, build, and demonstrate a plug system that would reliably meet key requirements.”

The plug needed to be able to be stored in limited space as well as be strong enough to withstand the external pressure from the water but also the internal pressure of the air inside the plug. These requirements led the project team to use a high-strength fabric construction similar to the technology used to land the Mars Rover on the harsh planet surface.

The plug was tested at ILC Dover’s facilities on a full-size replica subway tunnel. “We tested several configurations of the plug during the program to eventually identify the design that worked best in the tunnel environment,” said David Cadogan, ILC Dover’s director of engineering and product development. “The most challenging aspects of the design, aside from having it withstand all of that pressure, was getting the plug to deploy and then seal the tunnel in a completely repeatable fashion. Then, finding the right design to allow it fit into a very small container mounted in the tunnel.”

In final tests the RTP held back water for a full 21 days. “That was the final proof that we had met every requirement for the RTP system,” said Cadogan.

The research team has also explored other uses for the technology and  has developed additional tools needed to keep transit systems and citizens dry and safe during a terrorist attack or storm.

“Spinoff technologies based on the plug, include covers for subway stairwells and fabric flood walls that can be deployed in an instant during an emergency. More than 20 stairwell covers have already been installed in lower Manhattan as part of the New York City subway system's Super Storm Sandy recovery efforts," said Fortune, “With the RTP, we are capable of controlling the vastness of danger, damage and even inconvenience to the public due to flooding events.”

Click here to see a time-lapse video of the tunnel plug inflating.